One resource that I often recommend to new AdWords users is Andrew Goodman's "21 Powerful Google AdWords Tips and Techniques." (I apologize in advance - the Web page is a beast.)

We purchased a version of this eBook after we had developed a large AdWords account for our company. After reading it, I wish we had bought it sooner.

The book shares many great tips for maximizing your results with Google AdWords. From improving click-through rate to lowering your average cost per click, this book should help you build a solid AdWords account.

The cost of the book is $69 - I know it could have saved us at least that much had we purchased it when we first got into Google AdWords. If you are new to AdWords or are just looking for a refresher, I would recommend buying a copy.